1. Field of the Invention
This invention relates to conductive polymers comprising silicon-containing polymers, such as polysilanes, poly(di-silanylenephenylenes) and the like, which are particularly useful as electrodes for batteries, solar cells and boxes for electromagnetic shields. The invention also relates to a process for preparing such polymers.
2. Description of the Prior Art
In recent years, it has been found that doping of polyacetylene with electron acceptors or electron donors results in a charge transfer forming reaction, thereby developing high electric conductivity based on the electron conduction. Attention has now been paid to conductive organic polymer compounds such as polyacetylene, polyphenylene, polypyrrole, polyaniline and polythiophene for use as materials capable of forming highly conductive films.
However, these organic polymer compounds are not molten or fused and are poor in shaping properties. Accordingly, the following problems are involved. Where these polymers are formed into films according to a vapor phase polymerization process or an electrolytic polymerization process, limitation is inevitably placed on the shape of the resultant film, which depends on the shape of a reactor container or an electrode. In addition, when doped with electron acceptors or electron donors, the polymers suffer considerable degradation, thus presenting problems with practical applications.
On the other hand, silicon-containing polymers contain silicon atoms, so that they are more metallic in nature and exhibit greater non-electron-localizing properties than those polymers containing carbon atoms. In addition, such polymers are highly resistant to heat, are flexible and have good thin film-forming properties, thus being very interesting polymers. However, few silicon-containing polymers have been known as having high conductivity. Only Ishikawa et al proposed highly conductive polymers wherein disilanylenephenylene polymers are doped with fluorine compounds such as SbF.sub.5, AsF.sub.5 and the like (M. Ishikawa et al., J. Organometallics, 6, 1673 (1987); J. Organomet. Chem., 369, C18 (1989); Organometallics, 8, 2741 (1989); Macromolecules, 24, 2106 (1991)). However, SbF.sub.5, AsF.sub.5 and the like are so toxic that they are undesirable to handle. Further, they necessitate a complicated doping procedure.
Therefore, studies have been made to dope ferric chloride (FeCl.sub.3) which is less toxic and easier in handling than the fluorine compounds such as SbF.sub.5, AsF.sub.5 and the like. For instance, Corriu et al proposed doping with FeCl.sub.3 by mixing the polymer and FeCl.sub.3 in a solution (R. J. Corriu et al., J. Organomet. Chem., 417, C50 (1991)). This procedure is a wet doping method which requires flammable solvents and has the problem that satisfactorily high electric conductivity cannot be imparted to the polymers.